In the fabrication of semiconductor devices, a semi-conducting wafer must be processed in a large number of processing steps for producing various integrated circuits on chips. These processing steps may amount to as many as several hundred. The various processing steps are conducted in a large variety of processing, machines for carrying out chemical or physical reactions on the semi-conducting wafer. In the various fabrication steps, a large number of reactant gases are used. The reactant gases and their reaction products frequently encountered in the semiconductor fabrication industry may be highly flammable. For instance, the highly flammable gases may include silane, hydrogen and various other hydrocarbon gases. An effluent gas from the process machine must therefore be treated either in a chemical process or in a physical absorption or condensation process before it is released into a factory exhaust system and subsequently into the atmosphere.
The high flammability gases, which are normally of high boiling temperature or high boiling temperature components of other gases, present a serious processing hazard in the semiconductor fabrication facility. When such flammable gases are inadvertently, or accidentally ignited either in the chamber of a process machine or in a conduit connecting between the chamber and a flammable gas supply source, extremely serious consequences can result from such mishaps. Major fires have occurred in recent years in semiconductor fabrication facilities which result in serious personal injuries and equipment losses leading to a complete shut-down of the fabrication facility. The inadvertent or accidental ignition of a highly flammable gas can be caused by static electric charges, sparks produced by moving mechanical components or the self-igniting of flammable gases when exposed to high temperatures or oxygen environment.
The flammable gases that pose serious fire hazard may include those which are used as reactant gases and those which are by-products of a chemical reaction occurring in a reaction chamber. Since the exhaust conduits for the individual process machines are normally connected to a single factory exhaust, i.e., all the exhaust conduits from the various process machines are interconnected together in a fabrication facility, the spread of fire or explosion in the conduits can be extremely rapid and wide spread. For instance, a single fire started in a process machine can spread almost instantly to a large number of process machines and gas conveying conduits. The extent of damage to a semiconductor fabrication plant caused by a single fire started in a conduit or in a process machine can be astronomical as measured by the loss of human lives, bodily injuries and property damages.
After the occurrence of a fire in a fabrication facility, the recovery or clean-up procedure can be extremely laborious and time consuming. This is because the large amount of contaminating particles and debris generated during the fire which contaminates all the gas conveying conduits and the process chambers. It is not unusual that, after a major fire has erupted in a semiconductor fabrication facility, at least several months of production time is lost due to the clean-up and the refurbishing of damaged equipment.
It is therefore an object of the present invention to provide an apparatus and a method for stopping the propagation of an ignited flammable gas in a conduit that can be instantly effective upon the entering of a flame into the conduit without time delay that would otherwise be required in shutting off gas supply valves.
It is another object of the present invention to provide an apparatus for stopping the propagation of an ignited flammable gas in a conduit by utilizing a bullet means suspended in the conduit.
It is a further object of the present invention to provide an apparatus for stopping the propagation of an ignited flammable gas in a conduit by utilizing a bullet means which is deployable instantaneously when a flame enters a cavity of the conduit.
It is another further object of the present invention to provide an apparatus for stopping the propagation of an ignited flammable gas in a conduit by providing a mounting means fixedly attached inside a cavity of the conduit and mounting a bullet means thereon.
It is still another object of the present invention to provide an apparatus for stopping the propagation of an ignited flammable gas in a conduit by providing a bullet means which has an outside diameter larger than the diameter of the internal passage in the conduit.
It is yet another object of the present invention to provide an apparatus for stopping the propagation of an ignited flammable gas in a conduit by providing a bullet means which has a tapered, outside profile such that when the bullet means is deployed upon ignition by a flame, the tapered contour blocks a passage in an inlet end of the conduit and thus stopping the propagation of the flame from traveling further upstream.
It is still another further object of the present invention to provide a method for stopping the propagation of an ignited flammable gas in a conduit by providing a conduit body equipped with a mounting means and a bullet means inside the conduit cavity which can be activated upon the detection of a flame.
It is yet another further object of the present invention to provide a method for stopping the propagation of an ignited flammable gas in a conduit by providing a bullet means suspended in the cavity of the conduit equipped with an explosive pack such that a head portion of the bullet means is propelled toward an inlet of the conduit upon ignition by a flame to frictionally engaging the passageway in the inlet and stop the propagation of the flame from traveling further upstream.